Page 1 of 2 12 LastLast
Results 1 to 10 of 12

Thread: Why spend time getting ltrims from -13 down to -4?

  1. #1
    Senior Member
    Join Date
    Mar 2006
    Posts
    180

    Default Why spend time getting ltrims from -13 down to -4?

    Just in theory...why? If the ltrims are all negative and are trimming the part throttle down to 14.63af, why care if they are -13 or in the Optimum range of 0 to -4.

    WOT is tuned with a wideband and spot on...so no hp to be gained...other than the fun factor of fine tuning...why do it?

  2. #2
    Lifetime Member SSpdDmon's Avatar
    Join Date
    Jun 2005
    Posts
    1,556

    Default

    Because that's the right way to do it. j/k

    It's really a good idea because different conditions that you may face will cause your trims to move. If you go just to get gas, you can/will notice a significant swing in the LTFTs. Personally, I see a swing of -10 or so from said gas trips...

  3. #3
    EFILive Distributor dfe1's Avatar
    Join Date
    Jan 2005
    Posts
    837

    Default

    Apparently GM doesn't think there's any reason to get the LTFTs down below -10 to -13 because that's what you find with many of the factory tunes. Seriously, aside from crowding the limit, exceptionally high LTFTs (positive or negative) can lead to some fuel usage and drivability issues. Chances are the trims won't be off the same amount at all points in the map so if the values in some cells are way off, they'll conflict with the values in adjacent cells (that aren't way off) and the trims can actually be incorrect during certain throttle transitions. The PCM can make corrections quickly enough to prevent most, if not all effects from being felt by the driver, but the resulting momentary holes in operating efficiency can increase fuel consumption and exhaust emissions. Also keep in mind that actual values used by the PCM are a blend of the values in adjacent cells.
    DigitalEFI- EFILive US Distributor
    sales@digitalefi.com
    678/344-1590

  4. #4
    Senior Member
    Join Date
    Mar 2006
    Posts
    180

    Default

    Obviously, less the delta in most given, data driven equations. However, I'm still trying to find a substantive reason to spend time doing an auto VE tune. Again, 0-4 is where it "should" be if you're going to effect the tune....but I have not found a good reason to do it with concrete results...."potentially" better driveability/gasmileage, etc isn't enough motive since mine is "fine".

    Show me the real "whys".

    Also, this is for feedback only........I'm trying to learn why to fix something that may not need a fix.

    TIA

  5. #5
    EFILive Distributor dfe1's Avatar
    Join Date
    Jan 2005
    Posts
    837

    Default

    You're going to find a wide range of opinions on this, but I don't disagree with you. I've had a number of vehicles that ran great with LTFTs off by a good bit and others that didn't run as well as they should have, yet had LTFTs really close. As far as I'm concerned, all that really matters is how well a car runs. As far as supplying "concrete" reasons why LTFTs should be within a particular range, I don't have any. I'm sure some people would criticize my tunes for not being close enough in some areas, but I'm not concerned with that. As long as air/fuel ratios are on target and an engine produces the kind of power it should, and the vehicle owner is happy, that's all that matters. There's also a difference between tuning for a paying customer and for yourself or a friend. While everyone wants a "perfect" tune, few people are prepared to pay for the time it takes to do one. But if you're tuning for yourself, you can take as much time as you want-- and you'll always have a satisfied customer.
    DigitalEFI- EFILive US Distributor
    sales@digitalefi.com
    678/344-1590

  6. #6
    Unknown Zone TAQuickness's Avatar
    Join Date
    Jan 2005
    Posts
    2,940

    Default

    Quote Originally Posted by onfire
    Obviously, less the delta in most given, data driven equations. However, I'm still trying to find a substantive reason to spend time doing an auto VE tune. Again, 0-4 is where it "should" be if you're going to effect the tune....but I have not found a good reason to do it with concrete results...."potentially" better driveability/gasmileage, etc isn't enough motive since mine is "fine".

    Show me the real "whys".

    Also, this is for feedback only........I'm trying to learn why to fix something that may not need a fix.

    TIA

    If you are happy with what you have, then what's the problem?

    for grins and giggles, use the scan tool to reset your trims and see how she runs.

  7. #7
    Forum tyhee Site Admin GMPX's Avatar
    Join Date
    Apr 2003
    Posts
    12,780

    Default

    If it means anything, I don't even use STFT's, my O2's are there to fill in the holes!. My engine does not like 15.5:1 and higher AFR's, it tends to start to miss a little (might be the original 60,000mile plugs leads too ).
    Anyway, in closed loop the high end of the swing would sometimes hit that unhappy AFR point and you could feel it, well, I could anyway .
    What am I saying?, well, as DFE1 has pointed out, stock LS1's have LTFT's all over the place, my car with full open loop and Autotuned runs pretty much 14.5 - 14.8:1 everywhere when not in WOT, with STFT & LTFT's who knows where this would be at!.

    Cheers,
    Ross
    Need official EFILive help, please go here.
    For tuning support please post your questions on this forum (or other auto forums).
    Sorry if I don't respond to your PM, don't take it personal.


  8. #8
    Senior Member
    Join Date
    Mar 2006
    Posts
    180

    Default

    Quote Originally Posted by TAQuickness
    If you are happy with what you have, then what's the problem?

    for grins and giggles, use the scan tool to reset your trims and see how she runs.

    No problems...just researching the "whys" as a devil's advocate before I plunge ahead....best way to learn how something works.

    I'm a newbie to EFI Live, but so far I really love how it works and some of the changes I've made have worked very well....most impressed the the software.

    I'm taking baby steps before I take the real plunge and change the OS. What I'm doing now would drive the purists crazy. Twin turbo ls1 with a 1999 OS using PE vs RPM to get the wot to 11.8 : 1. Ltrims are between -6 and -13 in all cells so cell 22 goes to 0 at wot. Everything is working well so far....I'm trying to convince myself to change to a 2002 OS and SD.....but I'll probably do an auto VE map first for more of a learning curve before I play with SD....

    I appreciate all of the comments....helps a lot...keep'em coming.

  9. #9
    Joe (Moderator) joecar's Avatar
    Join Date
    Apr 2003
    Posts
    27,752

    Default

    Sounds like you're making serious power....
    Any pics...?

  10. #10
    Unknown Zone TAQuickness's Avatar
    Join Date
    Jan 2005
    Posts
    2,940

    Default

    Quote Originally Posted by onfire
    No problems...just researching the "whys" as a devil's advocate before I plunge ahead....best way to learn how something works.

    I'm a newbie to EFI Live, but so far I really love how it works and some of the changes I've made have worked very well....most impressed the the software.

    I'm taking baby steps before I take the real plunge and change the OS. What I'm doing now would drive the purists crazy. Twin turbo ls1 with a 1999 OS using PE vs RPM to get the wot to 11.8 : 1. Ltrims are between -6 and -13 in all cells so cell 22 goes to 0 at wot. Everything is working well so far....I'm trying to convince myself to change to a 2002 OS and SD.....but I'll probably do an auto VE map first for more of a learning curve before I play with SD....

    I appreciate all of the comments....helps a lot...keep'em coming.

    A very wise stance...

    I think you will see what I mean if you reset your trims.

    I've not had any luck with the NB's since my mods and run OLSD full time. I am slowly but surely working on a WB experiment to give CL a shot one last time.

Page 1 of 2 12 LastLast

Similar Threads

  1. A way to cheat and fix your strims/ltrims using Rtac Very quickly.
    By wait4me in forum RoadRunner Real-Time PCM Emulator
    Replies: 94
    Last Post: April 25th, 2016, 07:21 AM
  2. 1 more time
    By justin123 in forum Gen III V8 Specific
    Replies: 7
    Last Post: May 3rd, 2009, 11:21 AM
  3. PE vs RPM vs Time?
    By Highlander in forum Gen III V8 Specific
    Replies: 0
    Last Post: August 22nd, 2008, 01:12 AM
  4. Positive Ltrims In Cell 22
    By BowlingSS in forum General (Petrol, Gas, Ethanol)
    Replies: 10
    Last Post: March 17th, 2005, 02:15 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •